α-Olefin/vinylidene aromatic monomer and/or hindered aliphatic or cycloaliphatic vinylidene monomer interpolymers

ABSTRACT

The present invention relates to α-olefin/vinyl aromatic monomer interpolymers with characteristic signals in their carbon 13 NMR spectra. In particular, ethylene/styrene copolymers of the present invention have peaks in the carbon 13 NMR spectra which appear in the chemical shift range 43.70-44.25 ppm, preferably from 43.75-44.25 ppm and 38.0-38.5 ppm, said peaks being at least three times the peak to peak noise. The interpolymers are prepared by polymerizing the appropriate mixture of monomers in the presence of a catalyst such as racemic-(dimethylsilanediyl(2-methyl-4-phenylindenyl)) zirconium dichloride. The polymers of the present invention posses increased modulus as determined from both tensile stress/strain and dynamic mechanical data at comparable vinyl aromatic monomer levels.

The present invention concerns α-olefin/vinyl aromatic monomer and/orhindered aliphatic or cycloaliphatic vinyl or vinylidene monomerinterpolymers and a process for their preparation.

α-Olefin/vinyl aromatic monomer interpolymers have been prepared asdisclosed by James C. Stevens et al., in EP 0 416 815 A2 published Mar.13, 1991. In addition, M. Takeuchi et al., in EP 0 707 014 Al publishedApr. 17, 1996, disclose a process for producing an aromatic vinylcompound copolymer having a high degree of syndiotactic configuration inits aromatic vinyl chain. Also D. D. Devore et al., in WO 95/00526published on Jan. 5, 1995, disclose titanium or zirconium complexescontaining one and only one cyclic delocalized anionic π-bonded groupwherein the titanium or zirconium is in the +2 formal oxidation state.F. J. Timmers et al., in WO 96/04290 published on Feb. 15, 1996describes biscyclopentadienyl diene complexes of Group 4 transitionmetals. Finally K. W. McKay et al., in WO 96/07681, published on Mar.14, 1996, describes a thermoset elastomer comprising a crosslinkedpseudorandom or substantially random interpolymer of at least oneα-olefin, at least one vinyl aromatic compound, and at least one diene.The subject invention also provides a thermoplastic vulcanizatecomprising the thermoset elastomer as provided in a themoplasticpolyolefin matrix.

While these interpolymers have good properties, it is always desirableto have available polymers having an improvement in one or moreproperties.

The present invention relates to α-olefin/vinyl aromatic monomer and/orhindered aliphatic or cycloaliphatic vinyl or vinylidene monomerinterpolymers with characteristic signals in their carbon 13 NMRspectra. In particular, ethylene/styrene copolymers of the presentinvention have peaks detectable in the carbon 13 NMR spectra whichappear in the chemical shift range of 43.70-44.25, generally from43.75-44.25 ppm and 38.0-38.5 ppm said peaks being at least three timesthe peak to peak noise.

Another aspect of the present invention pertains to α-olefin/vinylaromatic monomer and/or hindered aliphatic or cycloaliphatic vinyl orvinylidene monomer interpolymers containing one or more tetrad sequencesconsisting of α-olefin/vinyl aromatic monomer or hindered aliphatic orcycloaliphatic vinyl or vinylidene monomer/vinyl aromatic monomer orhindered aliphatic or cycloaliphatic vinyl or vinylidenemonomer/α-olefin detectable by carbon 13 NMR spectroscopy wherein themonomer insertions of said tetrads occur exclusively in a 1,2 (head totail) manner.

The present invention also pertains to a process for preparing α-olefin/vinyl aromatic monomer and/or hindered aliphatic or cycloaliphaticvinyl or vinylidene monomer interpolymers, said process comprisingsubjecting to polymerizing conditions a combination of (1) α-olefin, (2)one or more vinyl aromatic monomers, and (3) optionally, one or morepolymerizable ethylenically unsaturated monomers other than (1) or (2)such as an α-olefin or diene; in the presence of a catalyst representedby the general formula:

wherein: each Cp is independently, each occurrence, a substitutedcyclopentadienyl group π-bound to M; E is C or Si; M is a group IVmetal, preferably Zr or Hf, most preferably Zr; each R is independently,each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl;each R′ is independently, each occurrence, H, halo, hydrocarbyl,hydrocarbyloxy, silahydrocarbyl, hydrocarbylsilyl, or two R′ groupstogether can be a hydrocarbyl substituted 1,3-butadiene; m is 1 or 2;and optionally, but preferably, in the presence of an activatingcocatalyst.

The polymers of the present invention possess increased modulus, asdetermined from both tensile stress/strain and dynamic mechanical data,at comparable vinyl aromatic monomer levels.

The present invention can comprise, consist of, or consist essentiallyof, all or only a portion of the aforementioned components, compounds,substituent groups or reaction steps. Components, compounds, substituentgroups or reaction steps can be eliminated singly or in multiples of anytwo or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a proton decoupled carbon 13 NMR spectrum (150 MHz) of example1 of the present invention, an ethylene/styrene copolymer containingESSE tetrad(s).

FIG. 2 is a proton decoupled carbon 13 NMR spectrum (150 MHz) ofcomparative experiment B an example of a “pseudorandom” ethylene/styrenecopolymer of the prior art.

FIG. 3 is a proton decoupled carbon 13 NMR spectrum (150 MHz) of example2 of the present invention, an ethylene/styrene copolymer containingESSE tetrad(s).

FIG. 4 is a proton decoupled carbon 13 NMR spectrum (150 MHz) of example3 of the present invention, an ethylene/styrene copolymer containingESSE tetrad(s).

The α-olefin/vinyl aromatic monomer interpolymers of the presentinvention are characterized using carbon 13 NMR spectroscopy. The carbon13 NMR spectra of ethylene/styrene interpolymers display signals in thechemical shift region 20 to 50 ppm as previously observed for pseudorandom ethylene/styrene interpolymers such as those described incopending application Ser. No. 08/481,791 filed Jun. 7, 1995 (equivalentto WO 96/04290 published Feb. 15, 1996). These signals previouslyobserved for the pseudo random interpolymers appear in the regions 25-26ppm, 27-28 ppm, 29-31 ppm, 34-35 ppm, 36.5-37.5 ppm, and 45-47 ppm. Inaddition, peaks between 40-47 ppm are sometimes observed. These otherpeaks between 40 and 47 ppm are believed to be due to the ubiquitouspolystyrene (aPS) which results from thermal polymerization of styrenemonomer to give an amorphous material which is present as a blend withthe ethylene/styrene copolymer. If aPS is present, its most prominentsignal is near 41 ppm.

The ethylene/styrene interpolymers contain additional signals withintensities greater than three times the peak to peak noise. Thesesignals appear in the chemical shift range 43.70-44.25 ppm, generallyfrom 43.75-44.25 ppm and 38.0-38.5 ppm. Specifically, major peaks areobserved at 44.1, 43.9 and 38.2 ppm. An Attached Proton Test (APT) NMRexperiment indicates that the signals in the chemical shift region43.70-44.25 ppm are methine carbons and the signals in the region38.0-38.5 ppm are methylene carbons.

In order to determine the carbon 13 NMR chemical shifts of theinterpolymers of the present invention, the following procedures andconditions are employed. A five to ten weight percent polymer solutionis prepared in a mixture consisting of 50 volume percent1,1,2,2-tetrachloroethane-d₂ and 50 volume percent 0.10 molar chromiumtris(acetylacetonate) in 1,2,4-trichlorobenzene. NMR spectra areacquired at 130° C. using an inverse gated decoupling sequence, a 90°pulse width and a pulse delay of five seconds or more. The spectra arereferenced to the isolated methylene signal of the polymer assigned at30.000 ppm.

While not wishing to be bound by any particular theory it is believedthat these new signals are due to sequences involving two head-to-tailvinyl aromatic monomer insertions preceded and followed by at least oneethylene insertion, for example, an ethylene/styrene/styrene/ethylenetetrad wherein the styrene monomer insertions of said tetrads occurexclusively in a 1,2 (head to tail) manner. It is understood by oneskilled in the art that for such tetrads involving a vinyl aromaticmonomer other than styrene, and an α-olefin other than ethylene, thatthe ethylene/vinyl aromatic monomer/vinyl aromatic monomer/ethylenetetrad will give rise to similar carbon 13 NMR peaks but with slightlydifferent chemical shifts.

The term “hydrocarbyl” means any aliphatic, cycloaliphatic, aromatic,aryl substituted aliphatic, aryl substituted cycloaliphatic, aliphaticsubstituted aromatic, or cycloaliphatic substituted aromatic groups. Thealiphatic or cycloaliphatic groups are preferably saturated. Likewise,the term “hydrocarbyloxy” means a hydrocarbyl group having an oxygenlinkage between it and the carbon atom to which it is attached.

The term “interpolymer” is used to indicate a polymer wherein at leasttwo different monomers are polymerized to make the interpolymer. Thisincludes copolymers, and terpolymers.

The term “substantially random” in the substantially random interpolymercomprising an a-olefin and a vinyl aromatic monomer as used herein meansthat the distribution of the monomers of said interpolymer can bedescribed by the Bernoulli statistical model or by a first or secondorder Markovian statistical model, as described by J. C. Randall inPOLYMER SEQUENCE DETERMINATION, Carbon 13 NMR Method, Academic Press NewYork, 1977, pp. 71-78. Preferably, the substantially random interpolymercomprising an α-olefin and a vinyl aromatic monomer does not containmore than 15 percent of the total amount of vinyl aromatic monomer inblocks of vinyl aromatic monomer of more than 3 units. More preferably,the interpolymer was not characterized by a high degree of eitherisotacticity or syndiotacticity. This means that in the 13C-NMR spectrumof the substantially random interpolymer the peak areas corresponding tothe main chain methylene and methine carbons representing either mesodiad sequences or racemic diad sequences should not exceed 75 percent ofthe total peak area of the main chain methylene and methine carbons.

Suitable catalysts which can be employed in the process of the presentinvention include those represented by the general formula:

wherein: each Cp is independently, each occurrence, a substitutedcyclopentadienyl group n-bound to M; E is C or Si; M is a group IVmetal, preferably Zr or Hf, more preferably Zr; each R is independently,each occurrence, hydrogen, hydrocarbyl, silahydrocarbyl, orhydrocarbylsilyl, containing up to 30 preferably from 1 to 20 morepreferably from 1 to 10 carbon or silicon atoms; each R′ isindependently, each occurrence, hydrogen, halo, hydrocarbyl,hyrocarbyloxy, silahydrocarbyl, hydrocarbylsilyl containing up to 30preferably from 1 to 20 more preferably from 1 to 10 carbon or siliconatoms or two R′ groups together can be a C₁₋₁₀ hydrocarbyl substituted1,3-butadiene; m is 1 or 2; and optionally, but preferably in thepresence of an activating cocatalyst. Particularly, suitable substitutedcyclopentadienyl groups include those illustrated by the formula:

wherein each R is independently, each occurrence, hydrogen, hydrocarbyl,silahydrocarbyl, or hydrocarbylsilyl, containing up to 30 preferablyfrom 1 to 20 more preferably from 1 to 10 carbon or silicon atoms or twoadjacent R groups together form a divalent derivative of such group.Preferably, R independently each occurrence is (including whereappropriate all isomers) hydrogen, methyl, ethyl, propyl, butyl, pentyl,hexyl, benzyl, phenyl or silyl or (where appropriate) two such R groupsare linked together forming a fused ring system such as indenyl,fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl, octahydrofluorenyl,or R susbstituted derivatives thereof.

Particularly preferred catalysts include, for example,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdichloride,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconium1,4-diphenyl-1,3-butadiene,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdi-C₁₋₄ alkyl,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdi-C₁₋₄ alkoxide, or any combination thereof.

Also included as catalysts useful for the preparation of the copolymersof the present invention are[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titaniumdimethyl, (1-indenyl) (tert-butyl amido)dimethylsilane titaniumdimethyl, ((3-tert-butyl) (1,2,3,4,5-η)-1-indenyl) (tert-butylamido)dimethylsilane titanium dimethyl, and((3-iso-propyl)(1,2,3,4,5-η)-1-indenyl) (tert-butyl amido)dimethylsilanetitanium dimethyl.

The term “activating cocatalyst” as used herein refers to a secondarycomponent of the catalyst able to cause the metal-containing complex tobecome effective as an addition polymerization catalyst or alternativelyto balance the ionic charge of a catalytically activated species.Examples of suitable activating cocatalysts for use herein include, forexample, aluminum compounds containing an Al—O bond such as thealkylalumoxanes, especially methylalumoxane; aluminum alkyls; aluminumhalides; aluminum alkyl halides; strong Lewis acids such as, forexample, tris(pentafluorophenyl)borane; the following salts whichcontain a compatible noninterfering counterion such astetrakis(pentafluorophenyl) borate, hydro(trihydrocarbyl)ammonium saltsand oxidizing agents, such as silver salts or ferrocenium salts; andmixtures of the foregoing.

Suitable α-olefins include, for example, α-olefins containing from 2 to20, preferably from 2 to 12, more preferably from 2 to 8 carbon atoms.Particularly suitable are ethylene, propylene, butene-1,4-methyl-1-pentene, hexene-1 and octene-1. Also suitable as are dienessuch as, for example, ethylidene norbornene, 1,4-hexadiene, andpiperylene; with ethylidene norbornene being preferred. The dienes areusually employed in amounts of from 1 to 5 mole percent of the polymer.

Suitable vinyl aromatic monomers include, for example, those representedby the formula Ar—CH═CH₂ wherein Ar is a phenyl group or a phenyl groupsubstituted with from 1 to 5 substituents selected from the groupconsisting of halo, C₁₋₄-alkyl, and C₁₋₄-haloalkyl. Exemplary monovinylaromatic monomers include styrene, vinyl toluene, t-butyl styrene,including all isomers of these compounds. Particularly suitable suchmonomers include styrene and lower alkyl- or halogen-substitutedderivatives thereof. Preferred monomers include styrene, the loweralkyl- or phenyl-ring substituted derivatives of styrene, such asortho-, meta-, and para-methylstyrene, the ring halogenated styrenes,para-vinyl toluene or mixtures thereof. A more preferred monovinylaromatic monomer is styrene.

Suitable hindered aliphatic or cycloaliphatic vinyl or vinylidenemonomers which can be employed herein include, for example, the additionpolymerizable vinyl or vinylidene monomers corresponding to the formula:

wherein A¹ is a sterically bulky, aliphatic or cycloaliphaticsubstituent of up to 20 carbons, R¹ is selected from the group ofradicals consisting of hydrocarbyl radicals containing from 1 to 4carbon atoms, preferably hydrogen or methyl; each R² is independentlyselected from the group of radicals consisting of hydrogen and alkylradicals containing from 1 to 4 carbon atoms, preferably hydrogen ormethyl; or alternatively R¹ and A¹ together form a ring system. By theterm “sterically bulky” is meant that the monomer bearing thissubstituent is normally incapable of addition polymerization by standardZiegler-Natta polymerization catalysts at a rate comparable withα-olefin polymerizations. Preferred hindered aliphatic or cycloaliphaticvinyl or vinylidene monomers are those in which one of the carbon atomsbearing ethylenic unsaturation is tertiary or quaternary substituted.Examples of such substituents include cyclic aliphatic groups such ascyclohexyl, cyclohexenyl, cyclooctenyl, or ring alkyl or arylsubstituted derivatives thereof, tert-butyl, norbornyl. Most preferredhindered aliphatic or cycloaliphatic vinyl or vinylidene monomers arevinyl cyclohexane, the various isomeric vinyl- ring substitutedderivatives of cyclohexene and substituted cyclohexenes, and5-ethylidene-2-norbornene. Especially suitable are 1-, 3-, and4-vinylcyclohexene.

The polymerization is conducted according to known techniques forZiegler-Natta or Kaminsky-Sinn type polymerizations. That is, themonomers-and catalyst are contacted at a temperature from −30° C. to250° C., at elevated or atmospheric pressures. The polymerization isconducted under an inert atmosphere which may be a blanketing gas suchas nitrogen or argon. Hydrogen may additionally be utilized in thecontrol of molecular weight through chain termination as is previouslyknown in the art. The catalyst may be used as is or supported on asuitable support such as alumina, MgCl₂ or silica to provide aheterogeneous supported catalyst. A solvent may be employed if desired.Suitable solvents include toluene, ethylbenzene, and excess vinylaromatic or olefin monomer. The reaction may also be conducted undersolution or slurry conditions, in a suspension utilizing aperfluorinated hydrocarbon or similar liquid, in the gas phase, ie.utilizing a fluidized bed reactor, optionally under condensing mode, orin a solid phase powder polymerization. A catalytically effective amountof the present catalyst and cocatalyst are any amounts that successfullyresult in formation of polymer. Such amounts may be readily determinedby the routine experimentation by the skilled artisan. Preferred amountsof catalyst and cocatalyst are sufficient to provide an equivalent ratioof addition polymerizable monomer:catalyst of from 1×10¹⁰:1 to 100:1,preferably from 1×10⁸:1 to 500:1, most preferably 1×10⁶:1 to 1,000:1.The cocatalyst is generally utilized in an amount to provide anequivalent ratio of cocatalyst:catalyst from 10,000:1 to 0.1:1,preferably from 1,000:1 to 1:1.

It is to be understood that the metal complex may undergo varioustransformations or form intermediate species prior to and during thecourse of a polymerization. Thus other precursors could possibly beconceived to achieve the same catalytic species.

The resulting polymeric product is recovered by filtering or othersuitable technique. Additives and adjuvants may be incorporated in thepolymers of the present invention in order to provide desirablecharacteristics. Suitable additives include pigments, UV stabilizers,antioxidants, blowing agents, lubricants, plasticizers,photosensitizers, and mixtures thereof.

On a limited basis, the vinyl aromatic monomer may insert into thepolymer chain in reverse order, ie. so as to result in two methylenegroups between the substituted polymer backbone moiety.

The interpolymers of one or more α-olefins and one or more monovinylaromatic monomers employed in the present invention-are substantiallyrandom polymers. These interpolymers usually contain from 1 to 65,preferably from 5 to 60, more preferably from 10 to 55 mole percent ofat least one vinyl aromatic monomer and from 35 to 99, preferably from40 to 95, more preferably from 45 to 90 mole percent of at least onealiphatic α-olefin having from 2 to 20 carbon atoms

The number average molecular weight (Mn) of the polymers andinterpolymers is usually greater than 1,000, preferably from 5,000 to1,000,000, more preferably from 10,000 to 500,000.

While preparing the substantially random interpolymer, an amount ofatactic vinyl aromatic homopolymer may be formed due tohomopolymerization of the vinyl aromatic monomer at elevatedtemperatures. In general, the higher the polymerization temperature, thehigher the amount of homopolymer that is formed. The presence of vinylaromatic homopolymer is in general not detrimental for the purposes ofthe present invention and may be tolerated. The vinyl aromatichomopolymer may be separated from the interpolymer, if desired, byextraction techniques such as selective precipitation from solution witha non solvent for either the interpolymer or the vinyl aromatichomopolymer. For the purpose of the present invention it is preferredthat no more than 20 weight percent, preferably less than 15 weightpercent based on the total weight of the interpolymers of vinyl aromatichomopolymer is present.

The substantially random interpolymers may be modified by typicalgrafting, hydrogenation, functionalizing, or other reactions well knownto those skilled in the art. The polymers may be readily sulfonated orchlorinated to provide functionalized derivatives according toestablished techniques.

Additives such as antioxidants (for example, hindered phenols such as,for example, Irganox® 1010 a registered trademark of CIBA-GEIGY),phosphites (for example, Irgafos® 168, a registered trademark ofCIBA-GEIGY), u. v. stabilizers, cling additives (for example, PIB),antiblock additives, slip agents, colorants, pigments, fillers can alsobe included in the interpolymers employed in the blends of and/oremployed in the present invention, to the extent that they do notinterfere with the enhanced properties discovered by Applicants.

The additives are employed in functionally equivalent amounts known tothose skilled in the art. For example, the amount of antioxidantemployed is that amount which prevents the polymer from undergoingoxidation at the temperatures and environment employed during storageand ultimate use of the polymers. Such amounts of antioxidants isusually in the range of from 0.01 to 10, preferably from 0.05 to 5, morepreferably from 0.1 to 2 percent by weight based upon the weight of thepolymer.

Similarly, the amounts of any of the other enumerated additives are thefunctionally equivalent amounts such as the amount to render the polymerantiblocking, to produce the desired amount of filler loading to producethe desired result, to provide the desired color from the colorant orpigment. Such additives can suitably be employed in the range of from0.05 to 50, preferably from 0.1 to 35 more preferably from 0.2 to 20percent by weight based upon the weight of the polymer. However, in theinstance of fillers, they could be employed in amounts up to 90 percentby weight based on the weight of the polymer.

The polymers of the present invention are useful as asphalt additives,films, adhesives, injection molded articles. The polymers of the presentinvention find particular utility in applications where a stiffermaterial response is desired, such as, for example, in some adhesiveformulations, and the manufacture of tougher single and multilayer filmsand certain molded articles.

The following examples are exemplary of the invention.

EXAMPLE 1

A. Polymer Preparation

A two liter stirred reactor was charged with 357 g (500 mL) of mixedalkane solvent (Isopar™-E a registered trademark of and available fromExxon Chemicals Inc.) and 461 g of styrene comonomer (500 mL). Hydrogenwas added to the reactor by differential pressure expansion from a 75 mLaddition tank, 51 delta psi (35 kPa). The reactor was heated to the runtemperature, 70° C., and the reactor was saturated with ethylene at thedesired pressure, 200 psig (1380 kPa). Catalyst and cocatalyst weremixed in a dry box by mixing the catalyst,racemic-(dimethylsilanediyl(2-methyl-4-phenylindenyl))zirconiumdichloride, and cocatalyst, methylalumoxane (MAO), in toluene in aninert atmosphere glove box. The resulting solution was transferred to acatalyst addition tank and injected into the reactor. The polymerizationwas allowed to proceed with ethylene on demand. Additional charges ofcatalyst and cocatalyst, if used, were prepared in the same manner andwere added to the reactor periodically. A total of 8.5 mmol of thecatalyst with 8.5 mmol of MAO was added. After the run time, 30 min, thepolymer solution was removed from the reactor. Volatiles were removedfrom the polymer in a reduced pressure vacuum oven at 135° C. for 20hrs. 26.1 g of polymer was isolated with a melt index (I₂) of 0.33.Proton NMR analysis indicates that the material was 11.1 mol % (31.7 wt%) styrene.

FIG. 1 was a proton decoupled carbon 13 NMR spectrum (150 MHz) of theabove prepared ethylene/styrene copolymer. This ethylene/styrenecopolymer contains ESSE tetrads as indicated by the peaks at 44.066,43.860 and 38.215.

Comparative Experiment A

Preparation of Copolymer

Polymer was prepared in a 400 gallon (1.512 m³) agitated semi-continuousbatch reactor. The reaction mixture consisted of approximately 250gallons (0.95 m³) of solvent comprising a mixture of cyclohexane (85 wtpercent) and isopentane (15 wt percent), and styrene. Prior to addition,solvent, styrene and ethylene were purified to remove water and oxygen.The inhibitor in the styrene was also removed. Inerts were removed bypurging the vessel with ethylene. The vessel was then pressurecontrolled to a set point with ethylene. Hydrogen was added to controlmolecular weight. Temperature in the vessel was controlled to set-pointby varying the jacket water temperature on the vessel. Prior topolymerization, the vessel was heated to the run temperature and thecatalyst components titanium(N-1,1-dimethylethyl)di-methyl(1-(1,2,3,4,5-1)-2,3,4,5-tetramethyl-2,4-cyclopentadien-1-yl)silan-aminato))(2-)N)-dimethyl,CAS# 135072-62-7, Tris(pentafluorophenyl)boron, CAS# 001109-15-5,modified methylalumoxane Type 3A, CAS# 146905-79-5, were flowcontrolled, on a mole ratio basis of 1/3/5 respectivily, combined andadded to the vessel. After starting, the polymerization was allowed toproceed with ethylene supplied to the reactor as required to maintainvessel pressure, with hydrogen addition to the headspace of the reactorto maintain a mole ratio with respect to the ethylene concentration. Atthe end of the run, the catalyst flow was stopped, ethylene was removedfrom the reactor, 1000 ppm of Irganox* 1010 anti-oxidant was then addedto the solution and the polymer was isolated from the solution. Theresulting polymer was isolated from solution by use of a devolatilizingextruder. In the case of the steam stripped material, additionalprocessing was required in extruder like equipment to reduce residualmoisture and any unreacted styrene.

Total Polymer Solvent Styrene H₂ Run in Total Wt % Sample loaded loadedPressure Temp. Added Time Solution Melt Styrene in Number lbs kg lbs kgPsig kPa ° C. Grams Hours Wt. % Index Polymer C.E. A* 1196 542 225 10270 483 60 7.5 6.1 7.2 0.03 29.8

Polymer Testing

Test parts and characterization data for the polymers of Example 1 andComparative Experiment A were generated according to the followingprocedures:

Compression Molding

Samples were melted at 190° C. for 3 minutes and compression molded at190° C. under 20,000 lb (9,072 kg) of pressure for another 2 minutes.Subsequently, the molten materials were quenched in a press equilibratedat room temperature.

Differential Scanning Calorimetry (DSC)

A Dupont DSC-2920 was used to measure the thermal transitiontemperatures and heat of transition for the interpolymers. In order toeliminate previous thermal history, samples were first heated to 200° C.Heating and cooling curves were recorded at 10° C./min. Melting (fromsecond heat) and crystallization temperatures were recorded from thepeak temperatures of the endotherm and exotherm, respectively. Thepercent crystallinity was estimated from the area under the secondheating endotherm, using a value of 292 J/g for fully crystallinepolyethylene.

Mechanical Testing

Tensile properties of the compression molded samples were measured usingan Instron 1145 tensile machine equipped with an extensiometer.ASTM-D638 micro-tensile samples were tested at a strain rate of 5 min⁻¹.The average of four tensile measurements was given. The yield stress andyield strain were recorded at the inflection point in the stress/straincurve. The Energy at break was the total area under the stress/straincurve.

Dynamic Mechanical Testing(DMS)

Data were generated on compression molded samples using a Rheometrics800E mechanical analyzer. Samples were run in torsion rectangulargeometry and purged under nitrogen. Data were collected using a forcedfixed frequency of 10 rad/sec, a torsional strain of 0.05% with datacollected isothermally at 4° C. intervals.

Comparative Example Experiment (A)* 1 Total wt % S 29.8 31.7 wt % PS** 11 wgt % S in ES 29.3 31 mole % S in ES 10.05 10.8 MFR, I₂ 0.03 0.33 Mw ×10⁻³ 240.9 308.6 Mw/Mn 2.04 4.48 DSC Tm, ° C. 70 124.2/101. 3/67.2 %Crystallinity 21.7 31.3 Tc, ° C. 58.2 97.5/51.1 Tg −17.2 — Stress/strainTensile Modulus, 20.0 60 MPa Yield % Strain 19.2 14.2 Yield Stress, MPa2.7 4.2 % Strain at Break 397.4 481.2 Stress at Break, 18.5 25.2 MPaEnergy at Break, 89.6 123.9 MPa DMS G′(−40° C.) × 10⁻⁷ 560 (56) 780 (78)dyne/cm² (Pa) G′(0° C.) × 10⁻⁷ 29 (2.9) 76 (7.6) dyne/cm² (Pa) G′(40°C.) × 10⁻⁷ 6.8 (0.68) 17 (1.7) dyne/cm² (Pa) Tg(G″max) ° C. −8 −7.9G″max at Tg × 10⁻⁸ 7.9 (0.79) 6.0 (0.60) dyne/cm²(Pa) Tg(tan δ max) ° C.−7.9 −7.9 *Not an example of the present invention **Determined byproton NMR techniques

The copolymer of example 1 also contains 1.2% high density PE fraction,as measured by ATREF techniques.

The copolymer of example 1 was compared with an ethylene/styrenecopolymer (comparative experiment A) having a pseudorandom structurehaving similar styrene comonomer content, and prepared using one of thecatalyst types disclosed in EP 0 416 815 A2.

In addition to the N.M.R. characterization, which show the uniquestyrene sequencing, there were identified performance characteristicswhich were significantly different for these materials.

The polymer structures were more heterogeneous, as evidenced by the morediffused, multiple melt transitions of the DSC data.

From dynamic mechanical data, although the polymers of the presentinvention have the same glass transition temperature, and a similarwidth of the loss peak, the structure shows a significantly reduced peakamplitude in the dynamic mechanical loss spectra.

The microstructural difference of the polymers of the present inventiontranslates into desirable mechanical property modifications, for examplethe increased modulus from both tensile stress/strain and dynamicmechanical data as compared to known ethylene/styrene interpolymers.

The polymers of the present invention could be preferred over the“pseudo-random” copolymers in applications where a stiffer, more elasticmaterial response was desirable, for example in some adhesiveformulations, and for the manufacture of tougher single and multilayerfilms.

Comparative Experiment B

The polymer sample was prepared in a continuous loop reactor whichbehaves as an isothermal CSTR. The reactor loop was composed of two ½Koch SMX static mixers, a custom, 1200 mL/min, magnetically coupled,Micropump® gear pump (available from and a registered trademark of theIdex Corporation) and assorted ½ Swagelok® tube fittings (available fromand a registered trademark of the Swagelok Corporation). The loop wasequipped with two inlets, one for metered flows of purified ethylene,hydrogen, toluene and mixtures of styrene and toluene, the other for theactive catalyst system. A pressure transducer on the feed inlet and aduel thermocouple in the loop provided inputs for PID control of reactorpressure and temperature via heating tapes on the static mixers and aResearch Control valve on the reactor outlet. An in-line viscometer fromCambridge Applied Scientifics monitors the outlet flow, which wassubsequently blended with a catalyst kill and cooled to ambienttemperature.

Solvents and gases were purified by passage through activated A-2alumina (liquids), activated A-204 alumina (gases) and activated Q-5reactant. The samples was prepared in a solvent that consists of 50percent by weight styrene monomer in toluene. The mixture was spargedwith helium for two hours and allowed to stand under a 20 psig (138 kPa)helium pad overnight.

Solvent/styrene mixture flow was 12.05 mL/min. The reactor was heated tothe desired run temperature (90° C. ) and catalyst flow begun. After thetemperature stabilizes, ethylene flow was started (1.475 g/min) andcatalyst and cocatalyst flows adjusted to achieve a steady reaction(0.225 mL/min). The hydrogen flow rate was 0.4 mg/min. The reactor wasthen allowed to line out until viscosity was stable (usually an hour)and collection of product begun.

The catalyst, [(η⁵-C₅Me₄)Me₂SiN^(t)Bu]TiMe₂, and cocatalyst, B(C₆F₅)₃used were as previously described in Comparative Experiment A. Thecatalyst and cocatalyst solutions were prepared in an inert atmosphereglove box as 0.00100 M in toluene. These solutions were pumped to thereactor.

The polymer solution was quenched upon exiting the reactor with atoluene solution consisting of a catalyst kill, isopropyl alcohol (15mL/L), and an antioxidant, Irganox 1010 (0.02 g/mL). The polymersolution was collected for 90 min. The cooled polymer solution wasplaced in a vacuum oven in which the temperature was slowly ramped from40° C. to 130° overnight. The polymer was cooled to below 50° C. beforeremoving it from the vacuum oven the next day. 126.9 g of polymer wasisolated. It had a melt index (I2) of 2.8 and was found by NMRspectroscopy to be 11 mole percent styrene.

FIG. 2 was a proton decoupled carbon 13 NMR spectrum (150 MHz) of theabove prepared “pseudo-random” ethylene/styrene copolymer. Thisethylene/styrene copolymer does not contain any ESSE tetrads asindicated by the absence of peaks at 44.066, 43.860 and 38.215.

EXAMPLE 2

Synthesis of Catalyst A, (1-indenyl)(tert-butyl amido)dimethylsilanetitanium dimethyl:

Preparation of Lithium indenide.

Indene (10.0 g, 0.0861 moles) was stirred in hexane (150 mL) as n-BuLi(0.8783 moles, 54.8 mL of 1.6 M solution in hexane) was added drop wise.The mixture was allowed to stir overnight at room temperature duringwhich time a solid precipitated. After the reaction period the solid wascollected via suction filtration, washed with hexane, dried undervacuum, and was used without further purification or analysis (9.35 g,89.1% yield).

Preparation of Dimethylsilyl(indenyl)(t-butylamine).

Lithium indenide (1.73 g, 0.014 moles) in THF (50 mL) was added dropwise to a solution of dimethylsilyl(t-butylamino)chloride (3.53 g, 0.021moles) in THF (75 mL). This mixture was allowed to stir for 6.5 hrs. Andthe volatile materials were removed. The residue was extracted andfiltered using hexane. Removal of the hexane resulted in the isolationof the desired product as an oil (2.53 g, 74.3% yield).

¹H NMR (CHCl₃): d-0.037 (s, 3H), 0.012 (s, 3H), 1.268 (s, 9H), 3.669 (s,1H), 6.740 (d, 1H), 6.959 (d, 1H), 7.190-7.310 (m, 2H), 7.500 (d, 1H),7.595 (d, 1H).

Preparation of Dimethylsilyl(indenyl)(t-butylamido)Li₂.

Dimethylsilyl(indenyl)(t-butylamino) (2.41 g, 0.0098 moles) was stirredin hexane (50 mL) as n-BuLi (0.0206 moles, 13.0 mL of 1.6 M solution inhexane) was added drop wise. This mixture was allowed to stir overnightduring which time a sticky solid precipitate formed. The volatilematerials were then removed and the resulting orange residue washed withpentane (2×10 mL). The solid was dried under vacuum and isolated as adeep orange solid which was used without further purification oranalysis (2.40 g, 94.5% yield).

Preparation of Dimethylsilyl(indenyl)(t-butylamido)TiCl₂.

Dimethylsilyl(indenyl) (t-butylamino)Li₂ (1.20 g, 0.0047 moles) in THF(20 mL)was added slowly to a slurry of TiCl₃(THF) (1.728 g, 0.0047moles) in THF (100 mL). After addition was complete this mixture wasallowed to stir for an additional 1 hr. PbCl₂ (0.65 g, 0.0024 moles) wasthen added as a solid and the mixture was allowed to stir for anadditional 1 hr. After the reaction period the volatile materials wereremoved and the residue extracted and filtered using toluene. Removal ofthe toluene resulted in the isolation of a dark residue which wasextracted with hexane and concentrated until solids were seen, thenplaced in a refrigerator at −20° C. for several hours. Solid wasisolated by cold filtration and dried under vacuum resulting in theisolation of a deep red-brown solid (1.16 g, 68.6% yield).

¹H NMR (C₆D₆): d0.306 (s, 3H), 0.519 (s, 3H), 1.320 (s, 9H), 6.255 (d,1H), 6.935 (m, 2H), 7.025 (t, 1H), 7.255 (d, 1H), 7.55 (d, 1H).

Preparation of Dimethylsilyl(indenyl)(t-butylamido)TiMe₂.

Dimethylsilyl(indenyl) (t-butylamido)TiCl₂ (0.90 g, 0.0025 moles) indiethylether (50 mL) as MeMgBr (0.0050 moles, 1.66 mL of 3.0 M indiethylether) was added drop wise. This mixture was allowed to stir for1 hr., where the volatile materials were removed and the residue andfiltered using hexane. Removal of the hexane resulted in the isolationof a dark yellow-green solid (0.60 g, 75.2% yield).

¹H NMR (C₆D₆): d-0.127 (s, 3H), 0.374 (s, 3H), 0.560 (s, 3H), 0.845 (s,3H), 1.464 (s, 9H), 6.060 (d, 1H), 6.885 (t, 1H), 7.010 (d, 1H), 7.085(m, 1H), 7.470 (t, 2H).

EXAMPLE 3

Synthesis of Catalyst B,[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]dimethyltitanium:

Preparation of 3,5,6,7-Tetrahydro-s-Hydrindacen-1(2H)-one.

Indan (94.00 g, 0.7954 moles) and 3-chloropropionyl chloride (100.99 g,0.7954 moles) were stirred in CH₂Cl₂ (300 mL) at 0° C. as AlCl₃ (130.00g, 0.9750 moles) was added slowly under a nitrogen flow. The mixture wasthen allowed to stir at room temperature for 2 hours. The volatilematerials were then removed. The mixture was then cooled to 0° C. andconcentrated H₂SO₄ (500 mL) slowly added. The forming solid had to befrequently broken up with a spatula as stirring was lost early in thisstep. The mixture was then left under nitrogen overnight at roomtemperature. The mixture was then heated until the temperature readingsreached 90° C. These conditions were maintained for a 2 hour period oftime during which a spatula was periodically used to stir the mixture.After the reaction period crushed ice was placed in the mixture andmoved around. The mixture was then transferred to a beaker and washedintermittently with H₂O and diethylether and then the fractions filteredand combined. The mixture was washed with H₂O (2×200 mL). The organiclayer was then separated and the volatile materials removed. The desiredproduct was then isolated via-recrystallization from hexane at 0° C. aspale yellow crystals (22.36 g, 16.3% yield).

¹H NMR (CDCl₃): d2.04-2.19 (m, 2H), 2.65 (t, ³J_(HH)=5.7 Hz, 2H),2.84-3.0 (m, 4H), 3.03 (t, ³J_(HH)=5.5 Hz, 2H), 7.26 (s, 1H), 7.53 (s,1H).

¹³C NMR (CDCl₃): d25.71, 26.01, 32.19, 33.24, 36.93, 118.90, 122.16,135.88, 144.06, 152.89, 154.36, 206.50.

GC-MS: Calculated for C₁₂H₁₂O 172.09, found 172.05.

Preparation of 1,2,3,5-Tetrahydro-s-indacen.

3,5,6,7-Tetrahydro-s-Hydrindacen-1(2H)-one (6.650 g, 38.61 mmol) andNaBH₄ (1.461 g, 38.61 mmol) were stirred in diethylether (100 mL) at 0°C. as EtOH (100 mL) was added slowly. This mixture was then allowed tostir overnight at room temperature. After the reaction period themixture was quenched by pouring over ice. The mixture was then acidified(pH=1) with 1M HCR. The organic layer was then separated and washed with1M HCl (2×100 mL) and the volatile materials removed. The residue wasthen redissolved in benzene and refluxed with p-toluensulfonic acid(0.10 g) in a Dean-Stark apparatus overnight removing H₂O as it wasformed. The reaction mixture was then washed with saturated NaHCO₃(2×100 mL). The organic fraction was then dried over MgSO₄, filtered,and the volatile materials removed resulting in the isolation of a paleyellow solid. Further purification via column chromatography resulted inthe isolation of the desired product as a pale yellow powder (1.200 g,19.9% yield).

¹H NMR (CDCl₃): d2.0-2.2 (m, 2H), 2.8-2.9 (m, 4H), 3.33 (s, 3H), 6.64(d, ³J_(HH)=5.4 Hz, 1H), 6.82 (d, ³J_(HH)=5.4 Hz, 1H), 7.25 (s, 1H),7.32 (s, 1H).

¹³C NMR (CDCl₃) d26.00, 32.67, 38.52, 116.77, 119.84, 131.94, 133.26,140.87, 142.11, 142.25, 143.32.

Preparation of 1,2,3,5-Tetrahydro-s-indacene, lithium salt.

1,2,3,5-Tetrahydro-s-indacen (1.790 g, 11.46 mmol) was stirred in hexane(50 mL) as nBuLi (13.75 mmol, 6.88 mL of 2.0 M solution in cyclohexane)was slowly added. This mixture was then allowed to stir overnight. Afterthe reaction period the solid was collected via suction filtration as anoff-white solid which was washed with hexane, dried under vacuum, andused without further purification or analysis (1.679 g, 90.3% yield).

Preparation ofN-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-s-indacen-1-yl)silanamine.

1,2,3,5-Tetrahydro-s-indacene, lithium salt (1.790 g, 11.04 mmol) in THF(25 mL) was added drop wise to a solution of ClSi(CH₃)₂-NH-tBu (2.157 g,16.56 mol) in THF (50 mL). This mixture was then allowed to stir at roomtemperature overnight. After the reaction period the volatile materialswere removed and the residue extracted and filtered using hexane. Theremoval of the hexane resulted in the isolation of the desired productas a yellow oil (2.799 g, 88.8% yield).

¹H NMR (CDCl₃) d-0.041 (s, 3H), 0.018 (s, 3H), 1.12 (s, 1H), 1.8-2.0 (m,2H), 2.7-3.0 (m, 4H), 3.51 (s, 1H), 6.62 (d, ³J_(HH)=5.2 Hz, 1H), 6.95(d, ³J_(HH)=4.9 Hz, 2H), 7.36 (s, 1H), 7.53 (s, 3H).

¹³C NMR (CDCl₃) d-0.42, −0.28, 26.42, 32.97, 33.21, 33.84, 48.24, 49.49,117.12, 119.33, 129.34, 135.50, 140.08, 141.03, 143.81, 144.29.

Preparation ofN-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-s-indacen-1-yl)silanamine,dilithium salt.

N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-s-indacen-1-yl)silanamine(2.799 g, 9.80 mmol) was stirred in hexane (75 mL) as nBuLi (21.57 mmol,10.78 mL of 2.0 M solution in cyclohexane) was added drop wise. Thismixture was then allowed to stir overnight during which time aprecipitate formed. After the reaction period the mixture was filteredand the desired product isolated as an off-white solid and used withoutfurther purification or analysis (1.803 g, 61.9% yield).

Preparation ofDichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titanium.

N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-s-indacen-1-yl)silanamine,dilithium salt (0.737 g, 2.48 mmol) in THF (25 mL) was added drop wiseto a slurry of TiCl₃(THF)₃ (0.919 g, 2.48 mmol) in THF (50 mL). Thismixture was allowed to stir for 1 hour. PbCl₂ (0.345 g, 1.24 mmol) wasthen added and the mixture allowed to stir for an additional 45 minutes.After the reaction period the volatile materials were removed and theresidue extracted and filtered using hexane. Removal of the hexaneresulted in the isolation of a brown powder. This residue was thendissolved in hexane and cooled to −78° C. The supernate was then removedagain resulting in the isolation of a brown powder. This procedure wasthen repeated at −15° C. resulting in the isolation of the desiredproduct as a brown powder (0.168 g, 16.8% yield).

¹H NMR (C₆D₆): d0.35 (s, 3H), 0.61 (s, 3H), 1.35 (s, 9H), 1.6-1.9 3 (m,2H), 2.5-2.8 (m, 4H), 6.28 (d, ³J_(HH)=3.1 Hz, 1H), 6.97 (d, ³J_(HH)=3.0Hz, 1H), 7.07 (s, 1H), 7.51 (s, 1H).

¹³C NMR (C₆D6): d0.86, 3.36, 26.42, 32.40, 32.52, 32.73, 62.60, 97.42,119.50, 120.50, 121.38, 135.28, 136.19, 147.56, 148.29.

Preparation ofDimethyl[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titanium.

Dichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-.eta.)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titanium(0.168 g, 0.420 mmol) was stirred in diethylether (50 mL) as MeMgBr(0.920 mmol, 0.31 mL of 3.0 M solution in diethylether) was added dropwise. This mixture was then stirred for 1 hour. After the reactionperiod the volatile materials were removed and the residue extracted andfiltered using hexane. Removal of the hexane resulted in the isolationof the desired product as a yellow solid (0.0978 g, 64.8% yield).

¹H NMR (C₆D6): d-0.13 (s, 3H), 0.40 (s, 3H), 0.62 (s, 3H), 0.86 (s, 3H),1.47 (s, 9H), 1.8-1.9 (m, 2H), 2.5-2.8 (m, 4H), 6.07 (d, ³J_(HH)=3.0 Hz,1H), 7.02 (d, ³J_(HH)=3.0 Hz, 1H), 7.31 (s, 1H), 7.40 (s, 1H).

¹³C NMR (C₆D₆): d1.97, 4.21, 26.83, 32.55, 32.65, 34.44, 53.13, 55.35,58.34, 90.84, 113.66, 119.93, 121.60, 126.53, 133.31, 143.96, 144.61.

Polymer Preparation:

A two liter stirred reactor was charged with the desired quantities ofmixed alkane solvent (Isopar-E available from Exxon Chemicals Inc., ca.500 ml) and of styrene comonomer (ca. 500 ml). Hydrogen was added to thereactor by differential pressure expansion from a 75 ml addition tank,(50 delta psi, 35 kPa). The reactor was heated to the run temperature,90° C., and the reactor was saturated with ethylene at the desiredpressure (200 psig, 1380 kPa). Catalyst and cocatalyst were mixed in adry box by mixing the catalyst with equimolar quantities of thecocatalyst, tris(pentafluorophenyl)borane, in toluene in an inertatmosphere glove box. The resulting solution was transferred to acatalyst addition tank and injected into the reactor. The polymerizationwas allowed to proceed with ethylene on demand. Additional charges ofcatalyst and cocatalyst, if used, were prepared in the same manner andwere added to the reactor periodically. At the end of the run, thereactor was pressurized up to ca. 400 psi (2760 kPa) with nitrogen. Thereactor was then emptied into a nitrogen purged vessel containing ca.100 ml isopropanol and 20 ml anti-oxidant solution in toluene (eitherIrganox 1010, 10 g/L or an Irganox 1010/Irgafos 168 mixture 6.7 g/L and3.4 g/L, respectively, both available from Ciba-Geigy). This wastransferred to a shallow pan and volatile materials were removed in anitrogen purged vacuum oven at ca. 130° C. for ca. 20 hours. The ovenwas cooled to at least 50° C. before removing samples. Polymer sampleswere packaged in storage bags and labeled with appropriate information

Total Run Polymer Catalyst Isopar E Styrene Time Yield Example(micromoles) (grams) (grams) (min.) (grams) 2 12.0 357 456 31 32.9 312.0 359 457 35 36.5

Ex 2, Catalyst was (1-indenyl)(tert-butyl amido)dimethylsilane titaniumdimethyl.

Ex 3, Catalyst was[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]dimethyltitanium.

FIGS. 3 and 4 were the proton decoupled carbon 13 NMR spectra (150 MHz)of the above prepared ethylene/styrene copolymers of examples 2 and 3respectively. The occurrence of ESSE tetrads were indicated by the peaksat 43.756 and 38.205 ppm for example 2 and 43.741, 38.149 and 38.086 ppmfor example 3.

We claim:
 1. An interpolymer comprising 1) at least one aliphatic alphaolefin having from 2 to 12 carbon atoms; and 2) at least one of a) avinyl aromatic monomer; or b) a hindered aliphatic or cycloaliphaticvinyl or vinylidene monomer; or c) a combination of at least one vinylaromatic monomer and at least one hindered aliphatic or cycloaliphaticvinyl or vinylidene monomer; and wherein said interpolymer; i) containsone or more tetrad sequences consisting of α-olefin/vinyl aromaticmonomer or hindered aliphatic or cycloaliphatic vinyl or vinylidenemonomer/vinyl aromatic monomer or hindered aliphatic or cycloaliphaticvinyl or vinylidene monomer/α-olefin insertions detectable by ¹³C NMRspectroscopy; and ii) wherein the monomer insertions of said tetradsoccur exclusively in a 1,2 (head to tail) manner.
 2. An interpolymer ofclaim 1 comprising (1) from 1 to 65 mole percent of either (a) at leastone vinyl aromatic monomer; or (b) at least one hindered aliphatic orcycloaliphatic vinyl or vinylidene monomer; or (c) a combination of atleast one vinyl aromatic monomer and at least one hindered aliphatic orcycloaliphatic vinyl or vinylidene monomer; and (2) from 35 to 99 molepercent of at least one aliphatic alpha olefin having from 2 to 12carbon atoms.
 3. An interpolymer of claim 1 comprising (1) from 1 to 65mole percent of styrene; and (2) from 35 to 99 mole percent of ethyleneor a combination of ethylene and at least one alpha olefin selected fromthe group consisting of propylene, 4methyl-1-pentene, butene-1, hexene-1or octene-1; and, optionally, further comprising (3) from 1 to 5 molepercent of a diene; wherein the total mole percent of the monomers is100 percent.
 4. An ethylene/styrene interpolymer having peaks of thecarbon 13 NMR spectra which appear in the chemical shift range43.70-44.25 ppm and 38.0-38.5 ppm, said peaks being at least three timesthe peak to peak noise.
 5. The ethylene/styrene interpolymer of claim 4having peaks of the carbon 13 NMR spectra which appear in the chemicalshift range 43.75-44.25 ppm and 38.0-38.5 ppm, said peaks being at leastthree times the peak to peak noise.
 6. A process for preparingα-olefin/vinyl aromatic monomer interpolymers said process comprisingsubjecting to Ziegler-Natta or Kaminsky-Sinn polymerization conditions,a combination of (1) one or more α-olefins, (2) one or more vinylaromatic monomers, and (3) optionally, one or more polymerizableethylenically unsaturated monomers other than (1) or (2); wherein (i)said α-olefin is ethylene or a combination of ethylene and one otherα-olefin having from 3 to 8 carbon atoms; (ii) said vinyl aromaticmonomer is styrene; (iii) said catalyst isracemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdichloride,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconium1,4-diphenyl-1,3-butadiene,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdi-C₁₋₄ alkyl,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl))zirconiumdi-C₁₋₄ alkoxide, or any combination thereof; and (iv) an activatingcocatalyst is employed and is selected from the group consisting ofalkylalumoxanes; aluminum alkyls; aluminum halides; aluminum alkylhalides; strong Lewis acids; salts which contain a compatiblenoninterfering counterion; oxidizing; and any combination of any two ormore of said cocatalysts.
 7. The process of claim 6 wherein (i) saidα-olefin is ethylene; (ii) said vinyl aromatic monomer is styrene; (iii)said catalyst is racemic-(dimethylsilanediyl)bis-(2-methyl-4-phenylindenyl))zirconium dichloride; and (iv) anactivating cocatalyst is employed and is methylalumoxane.
 8. A processfor preparing α-olefin/vinyl aromatic monomer interpolymers said processcomprising subjecting to Ziegler-Natta or Kaminsky-Sinn polymerizationconditions, a combination of (1) one or more α-olefins, (2) one or morevinyl aromatic monomers, and (3) optionally, one or more polymerizableethylenically unsaturated monomers other than (1) or (2); in thepresence of a catalyst selected from the group consisting of(N-(1,1-dimethylethyl)-1,1-dimethyl-1-((1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl)silanaminato(2-)-N)titaniumdimethyl, (1-indenyl)(tert-butyl amido)dimethylsilane titanium dimethyl,((3-tert-butyl) (1,2,3,4,5-η)-1-indenyl)(tert-butyl amido)dimethylsilanetitanium dimethyl, and ((3-iso-propyl)(1,2,3,4,5-η)-1-indenyl)(tert-butyl amido)dimethylsilane titaniumdimethyl.
 9. The process of claim 8 wherein (i) said α-olefin isethylene or a combination of ethylene and one other α-olefin having from3 to 8 carbon atoms; (ii) said vinyl aromatic monomer is styrene; (iii)an activating cocatalyst is employed and is selected from the groupconsisting of alkylalumoxanes; aluminum alkyls; aluminum halides;aluminum alkyl halides; strong Lewis acids; salts which contain acompatible noninterfering counterion; oxidizing; and any combination ofany two or more of said cocatalysts.